Eco-friendly AgInS2/ZnS quantum dot nanohybrids with tunable luminescent properties modulated by pH-sensitive biopolymer for potential solar energy harvesting applications
“…The surface charge of ZAIS nanocolloids was determined by zeta potential analysis (ZP = −51.5 ± 3.4 mV). The value is consistent with the predominance of negatively charged surface due to the carboxylic groups (R-COO - ) of anionic CMC ligand at physiological pH (pKa ~ 4.3) [11] , which promoted the electrostatic stabilization of the nanosystems. The hydrodynamic sizes (D h ) of the colloidal QDs were evaluated by DLS analysis.…”
Section: Resultssupporting
confidence: 77%
“…This is mostly associated with the size distribution of nanocrystals and the presence of sub-bandgap transitions arising from the intrinsic point defects (vacancies, interstitials, etc.) [11] . Fig.…”
Section: Resultsmentioning
confidence: 99%
“…The 3D plots ( Fig. 2 A) indicated that ZAIS QDs behaved as active fluorophores suitable for bioimaging ( e.g., cell-virus interactions) with a broad range of excitation wavelengths and emission in the green–red visible window, which are mostly ascribed to intrinsic crystallographic and surface defects [11] . ZAIS showed QY of 5%, which has already proven suitable as fluorescent nanoprobes for bioimaging applications [4] , [14] .…”
“…The surface charge of ZAIS nanocolloids was determined by zeta potential analysis (ZP = −51.5 ± 3.4 mV). The value is consistent with the predominance of negatively charged surface due to the carboxylic groups (R-COO - ) of anionic CMC ligand at physiological pH (pKa ~ 4.3) [11] , which promoted the electrostatic stabilization of the nanosystems. The hydrodynamic sizes (D h ) of the colloidal QDs were evaluated by DLS analysis.…”
Section: Resultssupporting
confidence: 77%
“…This is mostly associated with the size distribution of nanocrystals and the presence of sub-bandgap transitions arising from the intrinsic point defects (vacancies, interstitials, etc.) [11] . Fig.…”
Section: Resultsmentioning
confidence: 99%
“…The 3D plots ( Fig. 2 A) indicated that ZAIS QDs behaved as active fluorophores suitable for bioimaging ( e.g., cell-virus interactions) with a broad range of excitation wavelengths and emission in the green–red visible window, which are mostly ascribed to intrinsic crystallographic and surface defects [11] . ZAIS showed QY of 5%, which has already proven suitable as fluorescent nanoprobes for bioimaging applications [4] , [14] .…”
“…Although the seed-mediated growth route has led to larger, close-tostoichiometric, orthorhombic particles of lower size distribution, the chalcopyrite-type QDs resulting from the classical fast hot-injection route exhibit a significantly higher PLQY of (36 % vs. 8 %) with a longer lifetime exceeding 900 ns which are beneficial for bio-applications. 47,48 as well as the injection of ZnS precursors either at room temperature 38,49 or at higher temperature in heat-up, 19 microwave radiation assisted, 45,50 and hydrothermal 38,51 approaches. In contrast, here the ZnS shell was obtained through the simultaneous, dropwise addition of two distinct precursor solutions, one for zinc and one for sulfur, to the AIS cQDs at elevated temperature (96 °C).…”
Biocompatibility, biofunctionality, and chemical stability are essential criteria to be fulfilled by quantum dot (QD) emitters for bio-imaging and -sensing applications. In addition to these criteria, achieving efficient near-infrared (NIR) emission with nontoxic QDs remains very challenging. In this perspective, we developed water-soluble NIR-emitting AgInS 2 /ZnS core/shell (AIS/ ZnS) QDs functionalized with DNA. The newly established aqueous route relying on a two-step hot-injection synthesis led to highly luminescent chalcopyrite-type AIS/ZnS core/shell QDs with an unprecedented photoluminescence quantum yield (PLQY) of 55% at 700 nm and a long photoluminescence (PL) decay time of 900 ns. Fast and slow hot injection of the precursors were compared for the AIS core QD synthesis, yielding a completely different behavior in terms of size, size distribution, stoichiometry, and crystal structure. The PL peak positions of both types of core QDs were 710 (fast) and 760 nm (slow injection) with PLQYs of 36 and 8%, respectively. The slow and successive incorporation of the Zn and S precursors during the subsequent shell growth step on the stronger emitting cores promoted the formation of a three-monolayer thick ZnS shell, evidenced by the increase of the average QD size from 3.0 to 4.8 nm. Bioconjugation of the AIS/ZnS QDs with hexylthiol-modified DNA was achieved during the ZnS shell growth, resulting in a grafting level of 5−6 DNA single strands per QD. The successful chemical conjugation of DNA was attested by UV−vis spectroscopy and agarose gel electrophoresis. Importantly, surface plasmon resonance imaging experiments using complementary DNA strands further corroborated the successful coupling and the stability of the AIS/ZnS-DNA QD conjugates as well as the preservation of the biological activity of the anchored DNA. The strong NIR emission and biocompatibility of these AIS/ ZnS-DNA QDs provide a high potential for their use in biomedical applications.
“…Quantum dots (QDs) of ternary metal dichalcogenides (CuInS 2 and AgInS 2 ) are considered promising alternatives to binary cadmium and lead-containing chalcogenide QDs. Due to the low toxicity of ternary QDs, they are considered appropriate materials for the development of eco-friendly and bio-compatible devices [1,2,3,4,5,6,7]. The main feature of ternary QDs is their high tolerance to defect states, which leads to the formation of broadband absorption and emission.…”
Over recent years, quantum dots (QDs) based on ternary metal dichalcogenides have attracted a lot of attention due to their unique properties and a range of potential applications. Here, we review the latest studies on the optical properties of AgInS2/ZnS QDs with emphasis on their theoretical modeling, and present our investigations of electronic transitions invisible in unstructured absorption spectra of AgInS2/ZnS QDs. The analysis of the absorption, photoluminescence excitation (PLE), and magnetic circular dichroism (MCD) spectra of hydrophobic and hydrophilic AgInS2/ZnS QDs of different sizes enables us to determine positions of electron transitions in these QDs. We demonstrate that the use of the second derivative of PLE spectra provides more unequivocal data on the position of the energy transitions compared with the second derivative of absorption spectra. Analysis of the MCD spectra reveals that the magnetic field induces energy level mixing in AgInS2/ZnS QDs in contrast to the traditional Cd-based QDs, where MCD is associated only with removing degeneracy of the excited energy level.
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